Porogens, porogenated precursors and methods for using the same to provide porous organosilica glass films with low dielectric constants

ABSTRACT

A porous organosilica glass (OSG) film consists of a single phase of a material represented by the formula Si v O w C x H y F z , where v+w+x+y+z=100%, v is from 10 to 35 atomic %, w is from 10 to 65 atomic %, x is from 5 to 30 atomic %, y is from 10 to 50 atomic % and z is from 0 to 15 atomic %, wherein the film has pores and a dielectric constant less than 2.6. The film is provided by a chemical vapor deposition method in which a preliminary film is deposited from organosilane and/or organosiloxane precursors and pore-forming agents (porogens), which can be independent of, or bonded to, the precursors. The porogens are subsequently removed to provide the porous film. Compositions, such as kits, for forming the films include porogens and precursors. Porogenated precursors are also useful for providing the film.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to provisionalU.S. patent application Ser. No. 60/373,104 filed 17 Apr. 2002, and is adivisional application of U.S. patent application Ser. No. 10/409,468filed on 7 Apr. 2003, now U.S. Pat. No. 7,384,471, which, in turn, is acontinuation-in-part of U.S. patent application Ser. No. 10/150,798filed 17 May 2002, now U.S. Pat. No. 6,846,515, the entire disclosuresof which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to the field of low dielectricconstant materials produced by CVD methods as insulating layers inelectronic devices. The electronics industry utilizes dielectricmaterials as insulating layers between circuits and components ofintegrated circuits (IC) and associated electronic devices. Linedimensions are being reduced in order to increase the speed and memorystorage capability of microelectronic devices (e.g., computer chips). Asthe line dimensions decrease, the insulating requirements for theinterlayer dielectric (ILD) become much more rigorous. Shrinking thespacing requires a lower dielectric constant to minimize the RC timeconstant, where R is the resistance of the conductive line and C is thecapacitance of the insulating dielectric interlayer. C is inverselyproportional to spacing and proportional to the dielectric constant (k)of the interlayer dielectric (ILD). Conventional silica (SiO₂) CVDdielectric films produced from SiH₄ or TEOS (Si(OCH₂CH₃)₄,tetraethylorthosilicate) and O₂ have a dielectric constant k greaterthan 4.0. There are several ways in which industry has attempted toproduce silica-based CVD films with lower dielectric constants, the mostsuccessful being the doping of the insulating silicon oxide film withorganic groups providing dielectric constants in the range of 2.7-3.5.This organosilica glass is typically deposited as a dense film (density˜1.5 g/cm³) from an organosilicon precursor, such as a methylsilane orsiloxane, and an oxidant, such as O₂ or N₂O. Organosilica glass will beherein be referred to as OSG. As dielectric constant or “k” values dropbelow 2.7 with higher device densities and smaller dimensions, theindustry has exhausted most of the suitable low k compositions for densefilms and has turned to various porous materials for improved insulatingproperties.

The patents and applications which are known in the field of porous ILDby CVD methods field include: EP 1 119 035 A2 and U.S. Pat. No.6,171,945, which describe a process of depositing an OSG film fromorganosilicon precursors with labile groups in the presence of anoxidant such as N₂O and optionally a peroxide, with subsequent removalof the labile group with a thermal anneal to provide porous OSG; U.S.Pat. Nos. 6,054,206 and 6,238,751, which teach the removal ofessentially all organic groups from deposited OSG with an oxidizinganneal to obtain porous inorganic SiO₂; EP 1 037 275, which describesthe deposition of an hydrogenated silicon carbide film which istransformed into porous inorganic SiO₂ by a subsequent treatment with anoxidizing plasma; and U.S. Pat. No. 6,312,793 B1, WO 00/24050, and aliterature article Grill, A. Patel, V. Appl. Phys. Lett. (2001), 79(6),pp. 803-805, which all teach the co-deposition of a film from anorganosilicon precursor and an organic compound, and subsequent thermalanneal to provide a multiphase OSG/organic film in which a portion ofthe polymerized organic component is retained. In these latterreferences the ultimate final compositions of the films indicateresidual porogen and a high hydrocarbon film content (80-90 atomic %).It is preferable that the final film retain the SiO₂-like network, withsubstitution of a portion of oxygen atoms for organic groups.

All references disclosed herein are incorporated by reference herein intheir entireties.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a porous organosilica glass filmconsisting of a single phase of a material represented by the formulaSi_(v)O_(w)C_(x)H_(y)F_(z), where v+w+x+y+z=100%, v is from 10 to 35atomic %, w is from 10 to 65 atomic %, x is from 5 to 30 atomic %, y isfrom 10 to 50 atomic % and z is from 0 to 15 atomic %, wherein the filmhas pores and a dielectric constant less than 2.6.

The present invention further provides a chemical vapor depositionmethod for producing the porous organosilica glass film of theinvention, comprising: (a) providing a substrate within a vacuumchamber; (b) introducing into the vacuum chamber gaseous reagentsincluding at least one precursor selected from the group consisting ofan organosilane and an organosiloxane, and a porogen distinct from theat least one precursor; (c) applying energy to the gaseous reagents inthe vacuum chamber to induce reaction of the gaseous reagents to deposita preliminary film on the substrate, wherein the preliminary filmcontains the porogen, and the preliminary film is deposited withoutadded oxidants; and (d) removing from the preliminary film substantiallyall of the porogen to provide the porous film with pores and adielectric constant less than 2.6.

Still further provided is a chemical vapor deposition method forproducing the porous organosilica glass film of the invention,comprising: (a) providing a substrate within a vacuum chamber; (b)introducing into the vacuum chamber gaseous reagents including at leastone precursor selected from the group consisting of a organosilane andan organosiloxane, wherein the at least one precursor contains at leastone porogen bonded thereto; (c) applying energy to the gaseous reagentsin the vacuum chamber to induce reaction of the gaseous reagents todeposit a preliminary film on the substrate, wherein the preliminaryfilm contains the at least one porogen and a first quantity of methylgroups bonded to silicon atoms; and (d) removing from the preliminaryfilm at least a portion of the at least one porogen to provide theporous film with pores and a dielectric constant less than 2.6, whereinthe porous film contains a second quantity of methyl groups bonded tosilicon atoms, and the second quantity is more than 50% of the firstquantity.

Also provided are novel porogenated precursors for producing porousorganosilica glass films, including porogenated1,3,5,7-tetramethylcyclo-tetrasiloxanes, such asneohexyl-1,3,5,7-tetramethylcyclo-tetrasiloxane andtrimethylsilylethyl-1,3,5,7-tetramethylcyclo-tetrasiloxane.

Still further provided are novel compositions containing porogens andprecursors (porogenated and/or non-porogenated) for producing the filmsof the invention.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows infrared spectra of a film of the present invention usingthermally labile group admixed therewith before and after a post annealindicating the elimination of the thermally labile group;

FIG. 2 is an infrared spectrum of the film of the present inventionidentifying the peaks of the components of the film;

FIG. 3 is an infrared spectrum of ATP, a thermally labile group usefulas a pore forming additive in the present invention; and

FIG. 4 is a thermogravimetric analysis of the film of the presentinvention during anneal indicating weight loss resulting from the lossof thermally labile group from the film.

DETAILED DESCRIPTION OF THE INVENTION

Organosilicates are candidates for low k materials, but without theaddition of porogens to add porosity to these materials, their inherentdielectric constant is limited to as low as 2.7. The addition ofporosity, where the void space has an inherent dielectric constant of1.0, reduces the overall dielectric constant of the film, generally atthe cost of mechanical properties. Materials properties depend upon thechemical composition and structure of the film. Since the type oforganosilicon precursor has a strong effect upon the film structure andcomposition, it is beneficial to use precursors that provide therequired film properties to ensure that the addition of the neededamount of porosity to reach the desired dielectric constant does notproduce films that are mechanically unsound. Thus, the inventionprovides the means to generate porous OSG films that have a desirablebalance of electrical and mechanical properties. Other film propertiesoften track with electrical or mechanical properties.

Preferred embodiments of the invention provide a thin film materialhaving a low dielectric constant and improved mechanical properties,thermal stability, and chemical resistance (to oxygen, aqueous oxidizingenvironments, etc.) relative to other porous organosilica glassmaterials. This is the result of the incorporation into the film ofcarbon (preferably predominantly in the form of organic carbon, —CH_(x),where x is 1 to 3, more preferably the majority of C is in the form ofCH₃) whereby specific precursor or network-forming chemicals are used todeposit films in an environment free of oxidants (other than theoptional additive/carrier gas CO₂, to the extent it is deemed tofunction as an oxidant). It is also preferred that most of the hydrogenin the film is bonded to carbon.

Thus, preferred embodiments of the invention comprise: (a) about 10 toabout 35 atomic %, more preferably about 20 to about 30% silicon; (b)about 10 to about 65 atomic %, more preferably about 20 to about 45atomic % oxygen; (c) about 10 to about 50 atomic %, more preferablyabout 15 to about 40 atomic % hydrogen; (d) about 5 to about 30 atomic%, more preferably about 5 to about 20 atomic % carbon. Films may alsocontain about 0.1 to about 15 atomic %, more preferably about 0.5 toabout 7.0 atomic % fluorine, to improve one or more of materialsproperties. Lesser portions of other elements may also be present incertain films of the invention. OSG materials are considered to be low kmaterials as their dielectric constant is less than that of the standardmaterial traditionally used in the industry—silica glass. The materialsof the invention can be provided by adding pore-forming species orporogens to the deposition procedure, incorporating the porogens intothe as-deposited (i.e., preliminary) OSG film and removing substantiallyall of the porogens from the preliminary film while substantiallyretaining the terminal Si—CH₃ groups of the preliminary film to providethe product film. The product film is porous OSG and has a dielectricconstant reduced from that of the preliminary film as well as from ananalogous film deposited without porogens. It is important todistinguish the film of the present invention as porous OSG, as opposedto a porous inorganic SiO₂, which lacks the hydrophobicity provided bythe organic groups in OSG.

Silica produced by PE-CVD TEOS has an inherent free volume pore sizedetermined by positron annihilation lifetime spectroscopy (PALS)analysis to be about 0.6 nm in equivalent spherical diameter. The poresize of the inventive films as determined by small angle neutronscattering (SANS) or PALS is preferably less than 5 nm in equivalentspherical diameter, more preferably less than 2.5 nm in equivalentspherical diameter.

Total porosity of the film may be from 5 to 75% depending upon theprocess conditions and the desired final film properties. Films of theinvention preferably have a density of less than 2.0 g/ml, oralternatively, less than 1.5 g/ml or less than 1.25 g/ml. Preferably,films of the invention have a density at least 10% less than that of ananalogous OSG film produced without porogens, more preferably at least20% less.

The porosity of the film need not be homogeneous throughout the film. Incertain embodiments, there is a porosity gradient and/or layers ofvarying porosities. Such films can be provided by, e.g., adjusting theratio of porogen to precursor during deposition.

Films of the invention have a lower dielectric constant relative tocommon OSG materials. Preferably, films of the invention have adielectric constant at least 0.3 less than that of an analogous OSG filmproduced without porogens, more preferably at least 0.5 less. Preferablya Fourier transform infrared (FTIR) spectrum of a porous film of theinvention is substantially identical to a reference FTIR of a referencefilm prepared by a process substantially identical to the method exceptfor a lack of any porogen.

Films of the invention preferably have superior mechanical propertiesrelative to common OSG materials. Preferably, the base OSG structure ofthe films of the invention (e.g., films that have not had any addedporogen) has a hardness or modulus measured by nanoindentation at least10% greater, more preferably 25% greater, than that of an analogous OSGfilm at the same dielectric constant.

Films of the invention do not require the use of an oxidant to deposit alow k film. The absence of added oxidant to the gas phase, which isdefined for present purposes as a moiety that could oxidize organicgroups (e.g., O₂, N₂O, ozone, hydrogen peroxide, NO, NO₂, N₂O₄, ormixtures thereof), facilitates the retention of the methyl groups of theprecursor in the film. This allows the incorporation of the minimumamount of carbon necessary to provide desired properties, such asreduced dielectric constant and hydrophobicity. As well, this tends toprovide maximum retention of the silica network, providing films thathave superior mechanical properties, adhesion, and etch selectivity tocommon etch stop materials (e.g., silicon carbide, hydrogenated siliconcarbide, silicon nitride, hydrogenated silicon nitride, etc.), since thefilm retains characteristics more similar to silica, the traditionaldielectric insulator. Films of the invention may also contain fluorine,in the form of inorganic fluorine (e.g., Si—F). Fluorine, when present,is preferably contained in an amount ranging from 0.5 to 7 atomic %.

Films of the invention are thermally stable, with good chemicalresistance. In particular, preferred films after anneal have an averageweight loss of less than 1.0 wt %/hr isothermal at 425° C. under N₂.Moreover, the films preferably have an average weight loss of less than1.0 wt %/hr isothermal at 425° C. under air.

The films are suitable for a variety of uses. The films are particularlysuitable for deposition on a semiconductor substrate, and areparticularly suitable for use as, e.g., an insulation layer, aninterlayer dielectric layer and/or an intermetal dielectric layer. Thefilms can form a conformal coating. The mechanical properties exhibitedby these films make them particularly suitable for use in Al subtractivetechnology and Cu damascene or dual damascene technology.

The films are compatible with chemical mechanical planarization (CMP)and anisotropic etching, and are capable of adhering to a variety ofmaterials, such as silicon, SiO₂, Si₃N₄, OSG, FSG, silicon carbide,hydrogenated silicon carbide, silicon nitride, hydrogenated siliconnitride, silicon carbonitride, hydrogenated silicon carbonitride,boronitride, antireflective coatings, photoresists, organic polymers,porous organic and inorganic materials, metals such as copper andaluminum, and diffusion barrier layers such as but not limited to TiN,Ti(C)N TaN, Ta(C)N, Ta, W, WN or W(C)N. The films are preferably capableof adhering to at least one of the foregoing materials sufficiently topass a conventional pull test, such as ASTM D3359-95a tape pull test. Asample is considered to have passed the test if there is no discernibleremoval of film.

Thus in certain embodiments, the film is an insulation layer, aninterlayer dielectric layer, an intermetal dielectric layer, a cappinglayer, a chemical-mechanical planarization or etch stop layer, a barrierlayer or an adhesion layer in an integrated circuit.

Although the invention is particularly suitable for providing films andproducts of the invention are largely described herein as films, theinvention is not limited thereto. Products of the invention can beprovided in any form capable of being deposited by CVD, such ascoatings, multilaminar assemblies, and other types of objects that arenot necessarily planar or thin, and a multitude of objects notnecessarily used in integrated circuits. Preferably, the substrate is asemiconductor.

In addition to the inventive OSG products, the present inventionincludes the process by which the products are made, methods of usingthe products and compounds and compositions useful for preparing theproducts.

It is within the scope of the invention for a single species of moleculeto function as both the structure-former and porogen. That is, thestructure-forming precursor and the pore-forming precursor are notnecessarily different molecules, and in certain embodiments the porogenis a part of (e.g., covalently bound to) the structure-formingprecursor. Precursors containing porogens bound to them are sometimesreferred to hereinafter as “porogenated precursors”. For example, it ispossible to use neohexyl TMCTS as a single species, whereby the TMCTSportion of the molecule forms the base OSG structure and the bulky alkylsubstituent neohexyl is the pore forming species which is removed duringthe anneal process. Having the porogen attached to a Si species thatwill network into the OSG structure may be advantageous in achieving ahigher efficiency of incorporation of porogen into the film during thedeposition process. Furthermore, it may also be advantageous to have twoporogens attached to one Si in the precursor, such as indi-neohexyl-diethoxysilane, or two Si's attached to one porogen, such asin 1,4-bis(diethoxysilyl)cylcohexane, since the most likely bond tobreak in a plasma during the deposition process is the Si-Porogen bond.In this manner, reaction of one Si-Porogen bond in the plasma will stillresult in incorporation of the porogen in the deposited film. Additionalnon-limiting examples of preferred porogenated precursors include1-neohexyl-1,3,5,7-tetramethylcyclotetrasiloxane,1-neopentyl-1,3,5,7-tetramethylcyclotetrasiloxane,neopentyldiethoxysilane, neohexyldiethoxysilane,neohexyltriethoxysilane, neopentyltriethoxysilane andneopentyl-di-t-butoxysilane.

In certain embodiments of the materials in which a single or multipleporogen is attached to a silicon, it may be advantageous to design theporogen in such as way that when the film is cured to form the pores, apart of the porogen remains attached to the silicon to imparthydrophobicity to the film. The porogen in a precursor containingSi-Porogen may be chosen such that decomposition or curing leavesattached to the Si a terminal chemical group from the porogen, such as a—CH₃. For example, if the porogen neopentyl is chosen, it is expectedthat thermal annealing under the proper conditions would cause bondbreakage at the C—C bonds beta to the Si, that is the bond between thesecondary carbon adjacent to Si and the quaternary carbon of the t-butylgroup will thermodynamically be the most favorable bond to break. Underproper conditions this would leave a terminal —CH₃ group to satisfy theSi, as well as provide hydrophobicity and a low dielectric constant tothe film. Examples of precursors are neopentyl triethoxysilane,neopentyl diethoxy silane, and neopentyl diethoxymethylsilane.

The porogen in the deposited film may or may not be in the same form asthe porogen introduced to the reaction chamber. As well, the porogenremoval process may liberate the porogen or fragments thereof from thefilm. In essence, the porogen reagent (or porogen substituent attachedto the precursor), the porogen in the preliminary film, and the porogenbeing removed may or may not be the same species, although it ispreferable that they all originate from the porogen reagent (or porogensubstituent). Regardless of whether or not the porogen is unchangedthroughout the inventive process, the term “porogen” as used herein isintended to encompass pore-forming reagents (or pore-formingsubstituents) and derivatives thereof, in whatever forms they are foundthroughout the entire process of the invention.

Other aspects of this invention are novel organosilanes andorganosiloxanes. Novel porogen-containing (i.e., porogenated) materialssynthesized for use as low dielectric constant precursors, such asneohexyl TMCTS and trimethylsilylethyl TMCTS, may also have potentialapplications in other areas. The novel organosilanes of this inventionare easily prepared by hydrosilylation reactions of the olefin precursorwith either TMCTS or diethoxymethylsilane. For example, dropwiseaddition of either diethoxymethylsilane or TMCTS to a molar equivalentof distilled 3,3-dimethylbutene in the presence of chloroplatinic acidcatalyst affords the neohexyl-substituted silanes neohexyldiethoxymethylsilane and neohexyl tetramethylcyclotetrasiloxane in highyields.

Although the phrase “gaseous reagents” is sometimes used herein todescribe the reagents, the phrase is intended to encompass reagentsdelivered directly as a gas to the reactor, delivered as a vaporizedliquid, a sublimed solid and/or transported by an inert carrier gas intothe reactor.

In addition, the reagents can be carried into the reactor separatelyfrom distinct sources or as a mixture. The reagents can be delivered tothe reactor system by any number of means, preferably using apressurizable stainless steel vessel fitted with the proper valves andfittings to allow the delivery of liquid to the process reactor.

In certain embodiments, mixtures of different organosilanes and/ororganosiloxanes are used in combination. It is also within the scope ofthe invention to use combinations of multiple different porogens, andorganosilanes and/or organosiloxanes in combination with organosilaneand/or organosiloxane species with attached porogens. Such embodimentsfacilitate adjusting the ratio of pores to Si in the final product,and/or enhance one or more critical properties of the base OSGstructure. For example, a deposition utilizing diethoxymethylsilane(DEMS) and porogen might use an additional organosilicon such astetraethoxysilane (TEOS) to improve the film mechanical strength. Asimilar example may be the use of DEMS added to the reaction using theorganosilicon neohexyl-diethoxymethylsilane, where the neohexyl groupbound to the precursor functions as the porogen. A further example wouldbe the addition of di-tert-butoxy-diacetoxysilane to the reaction usingdi-tert-butoxymethylsilane and porogen. In certain embodiments, amixture of a first organosilicon precursor with two or fewer Si—O bondswith a second organosilicon precursor with three or more Si—O bonds, isprovided to tailor a chemical composition of the inventive film.

In addition to the structure forming species and the pore-formingspecies, additional materials can be charged into the vacuum chamberprior to, during and/or after the deposition reaction. Such materialsinclude, e.g., inert gas (e.g., He, Ar, N₂, Kr, Xe, etc., which may beemployed as a carrier gas for lesser volatile precursors and/or whichcan promote the curing of the as-deposited materials and provide a morestable final film) and reactive substances, such as gaseous or liquidorganic substances, NH₃, H₂, CO₂, or CO. CO₂ is the preferred carriergas.

Energy is applied to the gaseous reagents to induce the gases to reactand to form the film on the substrate. Such energy can be provided by,e.g., thermal, plasma, pulsed plasma, helicon plasma, high densityplasma, inductively coupled plasma, and remote plasma methods. Asecondary rf frequency source can be used to modify the plasmacharacteristics at the substrate surface. Preferably, the film is formedby plasma enhanced chemical vapor deposition. It is particularlypreferred to generate a capacitively coupled plasma at a frequency of13.56 MHz. Plasma power is preferably from 0.02 to 7 watts/cm², morepreferably 0.3 to 3 watts/cm², based upon a surface area of thesubstrate. It may be advantageous to employ a carrier gas whichpossesses a low ionization energy to lower the electron temperature inthe plasma which in turn will cause less fragmentation in the OSGprecursor and porogen. Examples of this type of low ionization gasinclude CO₂, NH₃, CO, CH₄, Ar, Xe, Kr.

The flow rate for each of the gaseous reagents preferably ranges from 10to 5000 sccm, more preferably from 30 to 1000 sccm, per single 200 mmwafer. The individual rates are selected so as to provide the desiredamounts of structure-former and pore-former in the film. The actual flowrates needed may depend upon wafer size and chamber configuration, andare in no way limited to 200 mm wafers or single wafer chambers.

It is preferred to deposit the film at a deposition rate of at least 50nm/min.

The pressure in the vacuum chamber during deposition is preferably 0.01to 600 torr, more preferably 1 to 15 torr.

The film is preferably deposited to a thickness of 0.002 to 10 microns,although the thickness can be varied as required. The blanket filmdeposited on a non-patterned surface has excellent uniformity, with avariation in thickness of less than 2% over 1 standard deviation acrossthe substrate with a reasonable edge exclusion, wherein e.g., a 5 mmoutermost edge of the substrate is not included in the statisticalcalculation of uniformity.

The porosity of the film can be increased with the bulk density beingcorrespondingly decreased to cause further reduction in the dielectricconstant of the material and extending the applicability of thismaterial to future generations (e.g., k<2.0).

The removal of substantially all porogen is assumed if there is nostatistically significant measured difference in atomic compositionbetween the annealed porous OSG and the analogous OSG without addedporogen. The inherent measurement error of the analysis method forcomposition (e.g., X-ray photoelectron spectroscopy (XPS), RutherfordBackscattering/Hydrogen Forward Scattering (RBS/HFS)) and processvariability both contribute to the range of the data. For XPS theinherent measurement error is Approx. +/−2 atomic %, while for RBS/HFSthis is expected to be larger, ranging from +/−2 to 5 atomic % dependingupon the species. The process variability will contribute a further +/−2atomic % to the final range of the data.

The following are non-limiting examples of Si-based precursors suitablefor use with a distinct porogen. In the chemical formulas which followand in all chemical formulas throughout this document, the term“independently” should be understood to denote that the subject R groupis not only independently selected relative to other R groups bearingdifferent superscripts, but is also independently selected relative toany additional species of the same R group. For example, in the formulaR¹ _(n)(OR²)_(4−n)—Si, when n is 2 or 3, the two or three R¹ groups neednot be identical to each other or to R².

-   -   R¹ _(n)(OR²)_(3−n)Si where R¹ can be independently H, C₁ to C₄,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, partially or fully fluorinated; R² can be independently        C₁ to C₆, linear or branched, saturated, singly or multiply        unsaturated, cyclic, aromatic, partially or fully fluorinated, n        is 1 to 3.        -   Example: diethoxymethylsilane, dimethyldimethoxysilane    -   R¹ _(n)(OR²)_(3−n)Si—O—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can        be independently H, C₁ to C₄, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R² and R⁴ can be independently C₁ to C₆, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, n is 1 to 3 and m is 1        to 3.        -   Example: 1,3-dimethyl-1,3-diethoxydisiloxane    -   R¹ _(n)(OR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₄, linear or branched, saturated, singly        or multiply unsaturated, cyclic, partially or fully fluorinated,        R² and R⁴ can be independently C₁ to C₆, linear or branched,        saturated, singly or multiply unsaturated, cyclic, aromatic,        partially or fully fluorinated, n is 1 to 3 and m is 1 to 3.        -   Example: 1,2-dimethyl-1,1,2,2-tetraethoxydisilane    -   R¹ _(n)(O(O)CR²)_(4−n)Si where R¹ can be independently H, C₁ to        C₄, linear or branched, saturated, singly or multiply        unsaturated, cyclic, partially or fully fluorinated; R² can be        independently H, C₁ to C₆, linear or branched, saturated, singly        or multiply unsaturated, cyclic, aromatic, partially or fully        fluorinated, n is 1 to 3.        -   Example: dimethyldiacetoxysilane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—O—SiR³ _(m)(O(O)CR⁴)_(3−m) where R¹ and        R³ can be independently H, C₁ to C₄, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² and R⁴ can be independently H, C₁ to C₆,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, aromatic, partially or fully fluorinated, n is 1 to 3        and m is 1 to 3.        -   Example: 1,3-dimethyl-1,3-diacetoxydisiloxane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—SiR³ _(m)(O(O)CR⁴)_(3−m) where R¹ and        R³ can be independently H, C₁ to C₄, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² and R⁴ can be independently H, C₁ to C₆,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, aromatic, partially or fully fluorinated, n is 1 to 3        and m is 1 to 3.        -   Example: 1,2-dimethyl-1,1,2,2-tetraacetoxydisilane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—O—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³        can be independently H, C₁ to C₄, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R² can be independently H, C₁ to C₆, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁴ can be        independently C₁ to C₆, linear or branched, saturated, singly or        multiply unsaturated, cyclic, aromatic, partially or fully        fluorinated, n is 1 to 3 and m is 1 to 3.        -   Example: 1,3-dimethyl-1-acetoxy-3-ethoxydisiloxane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³        can be independently H, C₁ to C₄, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R² can be independently H, C₁ to C₆, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated and R⁴ can be        independently C₁ to C₆, linear or branched, saturated, singly or        multiply unsaturated, cyclic, aromatic, partially or fully        fluorinated, n is 1 to 3 and m is 1 to 3.        -   Example: 1,2-dimethyl-1-acetoxy-2-ethoxydisilane    -   R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(4−(n+p))Si where R¹ can be        independently H, C₁ to C₄, linear or branched, saturated, singly        or multiply unsaturated, cyclic, partially or fully fluorinated,        R² can be independently C₁ to C₆, linear or branched, saturated,        singly or multiply unsaturated, cyclic, aromatic, partially or        fully fluorinated and R⁴ can be independently H, C₁ to C₆,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, aromatic, partially or fully fluorinated, and n is 1 to        3 and p is 1 to 3.        -   Example: methylacetoxy-t-butoxysilane    -   R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—O—SiR³        _(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ can be        independently H, C₁ to C₄, linear or branched, saturated, singly        or multiply unsaturated, cyclic, partially or fully fluorinated;        R² and R⁶ can be independently C₁ to C₆, linear or branched,        saturated, singly or multiply unsaturated, cyclic, aromatic,        partially or fully fluorinated, R⁴ and R⁵ can be independently        H, C₁ to C₆, linear or branched, saturated, singly or multiply        unsaturated, cyclic, aromatic, partially or fully fluorinated, n        is 1 to 3, m is 1 to 3, p is 1 to 3 and q is 1 to 3.        -   Example: 1,3-dimethyl-1,3-diacetoxy-1,3-diethoxydisiloxane    -   R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—SiR³        _(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ can be        independently H, C₁ to C₄, linear or branched, saturated, singly        or multiply unsaturated, cyclic, partially or fully fluorinated;        R², R⁶ can be independently C₁ to C₆, linear or branched,        saturated, singly or multiply unsaturated, cyclic, aromatic,        partially or fully fluorinated, R⁴, R⁵ can be independently H,        C₁ to C₆, linear or branched, saturated, singly or multiply        unsaturated, cyclic, aromatic, partially or fully fluorinated, n        is 1 to 3, m is 1 to 3, p is 1 to 3 and q is 1 to 3.        -   Example: 1,2-dimethyl-1,2-diacetoxy-1,2-diethoxydisilane    -   cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³        can be independently H, C₁ to C₄, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated, and x may be any integer from 2 to 8.        -   Examples: 1,3,5,7-tetramethylcyclotetrasiloxane,            Octamethylcyclotetrasiloxane

Provisos to all above precursor groups: 1) the reaction environment isessentially non-oxidative and/or has no oxidant added to the reactionmixture (other than the optional addition of CO₂ to the extent it isdeemed an oxidant), 2) a porogen is added to the reaction mixture, and3) a curing (e.g., anneal) step is used to remove substantially all ofthe included porogen from the deposited film to produce a k<2.6.

The above precursors may be mixed with porogen or have attachedporogens, and may be mixed with other molecules of these classes and/orwith molecules of the same classes except where n and/or m are from 0 to3.

-   -   Examples: TEOS, triethoxysilane, di-tertiarybutoxysilane,        silane, Disilane, di-tertiarybutoxydiacetoxysilane, etc

The following are additional formulas representing certain Si-basedprecursors suitable for use with a distinct porogen:

(a) the formula R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si where R¹ isindependently H or C₁ to C₄ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3 and p is 0 to 3;

(b) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—O—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R² and R⁶ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3 and m+q≦3;

(c) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R² and R⁶ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3 and m+q≦3;

(d) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁶ and R⁷ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3, and m+q≦3;

(e) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)CH_(4−t)where R¹ is independently H or C₁ to C₄ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3,and t is 2 to 4, provided that n+p≦4;

(f) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(p+p))Si)_(t)NH_(3−t)where R¹ is independently H or C₁ to C₄ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3 andt is 1 to 3, provided that n+p≦4;

(g) cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³ areindependently H, C₁ to C₄, linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinated, and x maybe any integer from 2 to 8;

(h) cyclic silazanes of the formula (NR₁SiR₁R₃)_(x), where R¹ and R³ areindependently H, C₁ to C₄, linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinated, and x maybe any integer from 2 to 8; and

(i) cyclic carbosilanes of the formula (CR₁R₃SiR₁R₃)_(x), where R¹ andR³ are independently H, C₁ to C₄, linear or branched, saturated, singlyor multiply unsaturated, cyclic, partially or fully fluorinated, and xmay be any integer from 2 to 8.

Although reference is made throughout the specification to siloxanes anddisiloxanes as precursors and porogenated precursors, it should beunderstood that the invention is not limited thereto, and that othersiloxanes, such as trisiloxanes and other linear siloxanes of evengreater length, are also within the scope of the invention.

The following are non-limiting examples of Si-based porogenatedprecursors, where the porogen material is one or more of R¹, R³ or R⁷:

-   -   R¹ _(n)(OR²)_(3−n)Si where R¹ can be independently H, C₁ to C₁₂,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, partially or fully fluorinated; R² can be independently        C₁ to C₁₂, linear or branched, saturated, singly or multiply        unsaturated, cyclic, aromatic, partially or fully fluorinated, n        is 1 to 3.        -   Example: diethoxy-neo-hexylsilane    -   R¹ _(n)(OR²)_(3−n)Si—O—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can        be independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R² and R⁴ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, n is 1 to 3 and m is 1        to 3.        -   Example: 1,3-diethoxy-1-neo-hexyldisiloxane    -   R¹ _(n)(OR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated, R² and R⁴ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, n is 1 to 3 and m is 1        to 3.        -   Example: 1,2-diethoxy-1-neo-hexyldisilane    -   R¹ _(n)(OR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated, R² and R⁴ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁷ is C₁ to C₁₂,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, partially or fully fluorinated, and bridges the two Si        atoms, n is 1 to 3 and m is 1 to 3.        -   Example: 1,4-bis(dimethoxysilyl)cyclohexane    -   R¹ _(n)(OR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated, R² and R⁴ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, n is 1 to 3 and m is 1        to 3.        -   Example: 1,2-diethoxy-1-neo-hexyldisilane    -   R¹ _(n)(O(O)CR²)_(4−n)Si where R¹ can be independently H, C₁ to        C₁₂, linear or branched, saturated, singly or multiply        unsaturated, cyclic, partially or fully fluorinated; R² can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, aromatic, partially or        fully fluorinated, n is 1 to 3.        -   Example: diacetoxy-neo-hexylsilane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—O—SiR³ _(m)(O(O)CR⁴)_(3−m) where R¹ and        R³ can be independently H, C₁ to C₁₂, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² and R⁴ can be independently H, C₁ to C₁₂,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, aromatic, partially or fully fluorinated, n is 1 to 3        and m is 1 to 3.        -   Example: 1,3-diacetoxy-1-neo-hexyldisiloxane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—SiR³ _(m)(O(O)CR⁴)_(3−m) where R¹ and        R³ can be independently H, C₁ to C₁₂, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² and R⁴ can be independently H, C₁ to C₁₂,        linear or branched, saturated, singly or multiply unsaturated,        cyclic, aromatic, partially or fully fluorinated, n is 1 to 3        and m is 1 to 3.        -   Example: 1,2-diacetoxy-1-neo-hexyldisilane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—O—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³        can be independently H, C₁ to C₁₂, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² can be independently H, C₁ to C₁₂, linear        or branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁴ can be        independently C₁ to C₁₂, linear or branched, saturated, singly        or multiply unsaturated, cyclic, aromatic, partially or fully        fluorinated, n is 1 to 3 and m is 1 to 3.        -   Example: 1-acetoxy-3,3-di-t-butoxy-1-neohexyldisiloxane    -   R¹ _(n)(O(O)CR²)_(3−n)Si—SiR³ _(m)(OR⁴)_(3−m) where R¹ and R³        can be independently H, C₁ to C₁₂, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated; R² can be independently H, C₁ to C₁₂, linear        or branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁴ can be        independently C₁ to C₁₂, linear or branched, saturated, singly        or multiply unsaturated, cyclic, aromatic, partially or fully        fluorinated, n is 1 to 3 and m is 1 to 3.        -   Example: 1-acetoxy-2,2-di-t-butoxy-1-neohexyldisilane    -   R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si where R¹ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated, R² can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated; R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, aromatic, partially or        fully fluorinated, and n is 1 to 3 and p is 1 to 3.        -   Example: acetoxy-t-butoxy-neo-hexylsilane    -   R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—O—SiR³        _(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R², R⁶ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁴, R⁵ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, aromatic, partially or        fully fluorinated, n is 1 to 3, m is 1 to 3, p is 1 to 3 and q        is 1 to 3.        -   Example: 1,3-diacetoxy-1,3-di-t-butoxy-1-neohexyldisiloxane    -   R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—SiR³        _(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m) where R¹ and R³ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, partially or fully        fluorinated; R², R⁶ can be independently C₁ to C₁₂, linear or        branched, saturated, singly or multiply unsaturated, cyclic,        aromatic, partially or fully fluorinated, R⁴, R⁵ can be        independently H, C₁ to C₁₂, linear or branched, saturated,        singly or multiply unsaturated, cyclic, aromatic, partially or        fully fluorinated, n is 1 to 3, m is 1 to 3, p is 1 to 3 and q        is 1 to 3.        -   Example: 1,2-diacetoxy-1,2-di-t-butoxy-1-neohexyldisilane    -   cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³        can be independently H, C₁ to C₁₂, linear or branched,        saturated, singly or multiply unsaturated, cyclic, partially or        fully fluorinated, and x may be any integer from 2 to 8.        -   Example: such as            1-neohexyl-1,3,5,7-tetramethylcyclotetrasiloxane

Provisos to all above groups: 1) the reaction environment is essentiallynon-oxidative and/or has no added oxidant (other than the optionaladdition of CO₂ to the extent it is deemed an oxidant) to the reactionmixture, 2) it is preferred that at least one of R¹, R³ and R⁷ have a C₃or larger hydrocarbon to act as pore former, and 3) a curing step (e.g.,thermal annealing) is used to remove at least a portion of the includedporogen, and preferably substantially all of the included porogen, fromthe deposited film to produce a dielectric constant less than 2.6.

The above precursors may be mixed with other molecules of these sameclasses and/or with molecules of the same classes except where n and/orm are from 0 to 3.

Alternatively, non-limiting examples of suitable Si-based porogenatedprecursors are represented by the following formulas:

(a) the formula R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si where R¹ isindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3 and p is 0 to 3, providedthat at least one of R¹ is substituted with a C₃ or larger hydrocarbonas the porogen;

(b) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—O—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵ and R⁶are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹ and R³ issubstituted with a C₃ or larger hydrocarbon as the porogen;

(c) the formula R¹ _(n)(OR²)_(p)((O)CR⁴)_(3−n−p)Si—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵ and R⁶are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹ and R³ issubstituted with a C₃ or larger hydrocarbon as the porogen;

(d) the formula R¹ _(n)(OR²)_(p)((O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵, R⁶, andR⁷ are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹, R³ and R⁷ issubstituted with a C₃ or larger hydrocarbon as the porogen;

(e) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)CH_(4−t)where R¹ is independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3, and t is 2to 4, provided that n+p≦4 and at least one of R¹ is substituted with aC₃ or larger hydrocarbon as the porogen;

(f) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)NH_(3−t)where R¹ is independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3 and t is 1 to3, provided that n+p≦4 and at least one of R¹ is substituted with a C₃or larger hydrocarbon as the porogen;

(g) cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³ areindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen;

(h) cyclic silazanes of the formula (NR₁SiR₁R₃)_(x), where R¹ and R³ areindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen; or

(i) cyclic carbosilanes of the formula (CR₁R₃SiR₁R₃)_(x), where R¹ andR³ are independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen.

The following are non-limiting examples of materials suitable for use asporogens of the invention:

1) Cyclic hydrocarbons of the general formula C_(n)H_(2n) where n=4-14,where the number of carbons in the cyclic structure is between 4 and 10,and where there can be a plurality of simple or branched hydrocarbonssubstituted onto the cyclic structure.

-   -   Examples include: cyclohexane, trimethylcyclohexane,        1-methyl-4(1-methylethyl)cyclohexane, cyclooctane,        methylcyclooctane, etc.

2) Linear or branched, saturated, singly or multiply unsaturatedhydrocarbons of the general formula C_(n)H_((2n+2)−2y) where n=2-20 andwhere y=0-n.

-   -   Examples include: ethylene, propylene, acetylene, neohexane,        etc.

3) Singly or multiply unsaturated cyclic hydrocarbons of the generalformula C_(n)H_(2n−2x) where x is the number of unsaturated sites in themolecule, n=4-14, where the number of carbons in the cyclic structure isbetween 4 and 10, and where there can be a plurality of simple orbranched hydrocarbons substituted onto the cyclic structure. Theunsaturation can be located inside endocyclic or on one of thehydrocarbon substituents to the cyclic structure.

-   -   Examples include cyclohexene, vinylcyclohexane,        dimethylcyclohexene, t-butylcyclohexene, alpha-terpinene,        pinene, 1,5-dimethyl-1,5-cyclooctadiene, vinyl-cyclohexene, etc.

4) Bicyclic hydrocarbons of the general formula C_(n)H_(2n−2) wheren=4-14, where the number of carbons in the bicyclic structure is between4 and 12, and where there can be a plurality of simple or branchedhydrocarbons substituted onto the cyclic structure.

-   -   Examples include, norbornane, spiro-nonane,        decahydronaphthalene, etc.

5) Multiply unsaturated bicyclic hydrocarbons of the general formulaC_(n)H_(2n−(2+2x)) where x is the number of unsaturated sites in themolecule, n=4-14, where the number of carbons in the bicyclic structureis between 4 and 12, and where there can be a plurality of simple orbranched hydrocarbons substituted onto the cyclic structure. Theunsaturation can be located inside endocyclic or on one of thehydrocarbon substituents to the cyclic structure.

-   -   Examples include camphene, norbornene, norbornadiene, etc.

6) Tricyclic hydrocarbons of the general formula C_(n)H_(2n−4) wheren=4-14, where the number of carbons in the tricyclic structure isbetween 4 and 12, and where there can be a plurality of simple orbranched hydrocarbons substituted onto the cyclic structure.

-   -   Examples include adamantane.

The invention further provides compositions for conducting the inventiveprocess. A composition of the invention preferably comprises:

(A) at least one porogenated precursor represented by:

(1) the formula R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si where R¹ isindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3 and p is 0 to 3, providedthat n+p≦4, and that at least one of R¹ is substituted with a C₃ orlarger hydrocarbon as the porogen;

(2) the formula R¹ _(n)(OR²)_(p)(O(O)C R⁴)_(3−n−p)Si—O—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵ and R⁶are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹ and R³ issubstituted with a C₃ or larger hydrocarbon as the porogen;

(3) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵ and R⁶are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹ and R³ issubstituted with a C₃ or larger hydrocarbon as the porogen;

(4) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₁₂ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁴, R⁵, R⁶, andR⁷ are independently C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3 and p is 0 to 3,provided that n+m≧1, n+p≦3, m+q≦3, and at least one of R¹, R³ and R⁷ issubstituted with a C₃ or larger hydrocarbon as the porogen; or

(5) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)CH_(4−t)where R¹ is independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3, and t is 2to 4, provided that n+p≦4 and at least one of R¹ is substituted with aC₃ or larger hydrocarbon as the porogen;

(6) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)NH_(3−t)where R¹ is independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² and R³ are independently C₁ to C₁₂ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3 and t is 1 to3, provided that n+p≦4 and at least one of R¹ is substituted with a C₃or larger hydrocarbon as the porogen;

(7) cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³ areindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen;

(8) cyclic silazanes of the formula (NR₁SiR¹R₃)_(x), where R¹ and R³ areindependently H or C₁ to C₁₂ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen; or

(9) cyclic carbosilanes of the formula (CR₁R₃SiR₁R₃)_(x), where R¹ andR³ are independently H or C₁ to C₁₂ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon, and x is any integer from 2 to 8, provided that at leastone of R¹ and R³ is substituted with a C₃ or larger hydrocarbon as theporogen; or

(B)(1) at least one precursor selected from the group consisting of:

(a) the formula R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si where R¹ isindependently H or C₁ to C₄ linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3 and p is 0 to 3;

(b) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—O—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R² and R⁶ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3 and m+q≦3;

(c) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R² and R⁶ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3 and m+q≦3;

(d) the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁶ and R⁷ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3, and m+q≦3;

(e) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)CH_(4−t)where R¹ is independently H or C₁ to C₄ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3,and t is 2 to 4, provided that n+p≦4;

(f) the formula (R¹ _(n)(OR²)_(p)(O(O)CR³)_(4−(n+p))Si)_(t)NH_(3−t)where R¹ is independently H or C₁ to C₄ linear or branched, saturated,singly or multiply unsaturated, cyclic, partially or fully fluorinatedhydrocarbon; R² is independently C₁ to C₆ linear or branched, saturated,singly or multiply unsaturated, cyclic, aromatic, partially or fullyfluorinated hydrocarbon, R³ is independently H, C₁ to C₆ linear orbranched, saturated, singly or multiply unsaturated, cyclic, aromatic,partially or fully fluorinated hydrocarbon, n is 1 to 3, p is 0 to 3 andt is 1 to 3, provided that n+p≦4;

(g) cyclic siloxanes of the formula (OSiR₁R₃)_(x), where R¹ and R³ areindependently H, C₁ to C₄, linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinated, and x maybe any integer from 2 to 8;

(h) cyclic silazanes of the formula (NR₁SiR₁R₃)_(x), where R¹ and R³ areindependently H, C₁ to C₄, linear or branched, saturated, singly ormultiply unsaturated, cyclic, partially or fully fluorinated, and x maybe any integer from 2 to 8; and

(i) cyclic carbosilanes of the formula (CR¹R₃SiR¹R₃)_(x), where R¹ andR³ are independently H, C₁ to C₄, linear or branched, saturated, singlyor multiply unsaturated, cyclic, partially or fully fluorinated, and xmay be any integer from 2 to 8, and

(B)(2) a porogen distinct from the at least one precursor, said porogenbeing at least one of:

(a) at least one cyclic hydrocarbon having a cyclic structure and theformula C_(n)H_(2n), where n is 4 to 14, a number of carbons in thecyclic structure is between 4 and 10, and the at least one cyclichydrocarbon optionally contains a plurality of simple or branchedhydrocarbons substituted onto the cyclic structure;

(b) at least one linear or branched, saturated, singly or multiplyunsaturated hydrocarbon of the general formula C_(n)H_((2n+2)−2y) wheren=2-20 and where y=0-n;

(c) at least one singly or multiply unsaturated cyclic hydrocarbonhaving a cyclic structure and the formula C_(n)H_(2n−2x), where x is anumber of unsaturated sites, n is 4 to 14, a number of carbons in thecyclic structure is between 4 and 10, and the at least one singly ormultiply unsaturated cyclic hydrocarbon optionally contains a pluralityof simple or branched hydrocarbons substituents substituted onto thecyclic structure, and contains endocyclic unsaturation or unsaturationon one of the hydrocarbon substituents;

(d) at least one bicyclic hydrocarbon having a bicyclic structure andthe formula C_(n)H_(2n−2), where n is 4 to 14, a number of carbons inthe bicyclic structure is from 4 to 12, and the at least one bicyclichydrocarbon optionally contains a plurality of simple or branchedhydrocarbons substituted onto the bicyclic structure;

(e) at least one multiply unsaturated bicyclic hydrocarbon having abicyclic structure and the formula C_(n)H_(2n−(2+2x)), where x is anumber of unsaturated sites, n is 4 to 14, a number of carbons in thebicyclic structure is from 4 to 12, and the at least one multiplyunsaturated bicyclic hydrocarbon optionally contains a plurality ofsimple or branched hydrocarbons substituents substituted onto thebicyclic structure, and contains endocyclic unsaturation or unsaturationon one of the hydrocarbon substituents; and/or

(f) at least one tricyclic hydrocarbon having a tricyclic structure andthe formula C_(n)H_(2n−4), where n is 4 to 14, a number of carbons inthe tricyclic structure is from 4 to 12, and the at least one tricyclichydrocarbon optionally contains a plurality of simple or branchedhydrocarbons substituted onto the cyclic structure.

In certain embodiments of the composition comprising a porogenatedprecursor, the composition preferably includes at least one porogenatedprecursor selected from the group consisting ofneohexyl-1,3,5,7-tetramethylcyclotetrasiloxane andtrimethylsilylethyl-1,3,5,7-tetramethylcyclotetrasiloxane.

In certain embodiments of the composition comprising a porogen-freeprecursor, the composition preferably comprises:

(a)(i) at least one precursor selected from the group consisting ofdiethoxymethylsilane, dimethoxymethylsilane, di-isopropoxymethylsilane,di-t-butoxymethylsilane, methyltriethoxysilane, methyltrimethoxysilane,methyltri-isopropoxysilane, methyltri-t-butoxysilane,dimethyldimethoxysilane, dimethyldiethoxysilane,dimethyldi-isopropoxysilane, dimethyldi-t-butoxysilane,1,3,5,7-tetramethylcyclotatrasiloxane, octamethyl-cyclotetrasiloxane andtetraethoxysilane, and (ii) a porogen distinct from the at least oneprecursor, said porogen being a member selected from the groupconsisting of alpha-terpinene, limonene, cyclohexane,1,2,4-trimethylcyclohexane, 1,5-dimethyl-1,5-cyclooctadiene, camphene,adamantane, 1,3-butadiene, substituted dienes and decahydronaphthelene;and/or

(b)(i) at least one precursor selected from the group consisting oftrimethylsilane, tetramethylsilane, diethoxymethylsilane,dimethoxymethylsilane, ditertiarybutoxymethylsilane,methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,methyltriacetoxysilane, methyldiacetoxysilane, methylethoxydisiloxane,tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane,dimethyldiacetoxysilane, bis(trimethoxysilyl)methane,bis(dimethoxysilyl)methane, tetraethoxysilane and triethoxysilane, and(ii) alpha-terpinene, gamma-terpinene, limonene, dimethylhexadiene,ethylbenzene, decahydronaphthalene, 2-carene, 3-carene, vinylcyclohexeneand dimethylcyclooctadiene.

Compositions of the invention can further comprise, e.g., at least onepressurizable vessel (preferably of stainless steel) fitted with theproper valves and fittings to allow the delivery of porogen,non-porogenated precursor and/or porogenated precursor to the processreactor. The contents of the vessel(s) can be premixed. Alternatively,porogen and precursor can be maintained in separate vessels or in asingle vessel having separation means for maintaining the porogen andprecursor separate during storage. Such vessels can also have means formixing the porogen and precursor when desired.

The porogen is removed from the preliminary (or as-deposited) film by acuring step, which can comprise thermal annealing, chemical treatment,in-situ or remote plasma treating, photocuring and/or microwaving. Otherin-situ or post-deposition treatments may be used to enhance materialsproperties like hardness, stability (to shrinkage, to air exposure, toetching, to wet etching, etc.), integrity, uniformity and adhesion. Suchtreatments can be applied to the film prior to, during and/or afterporogen removal using the same or different means used for porogenremoval. Thus, the term “post-treating” as used herein denotes treatingthe film with energy (e.g., thermal, plasma, photon, electron,microwave, etc.) or chemicals to remove porogens and, optionally, toenhance materials properties.

The conditions under which post-treating are conducted can vary greatly.For example, post-treating can be conducted under high pressure or undera vacuum ambient.

Annealing is conducted under the following conditions.

The environment can be inert (e.g., nitrogen, CO₂, noble gases (He, Ar,Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air, dilute oxygenenvironments, enriched oxygen environments, ozone, nitrous oxide, etc.)or reducing (dilute or concentrated hydrogen, hydrocarbons (saturated,unsaturated, linear or branched, aromatics), etc.). The pressure ispreferably about 1 Torr to about 1000 Torr, more preferably atmosphericpressure. However, a vacuum ambient is also possible for thermalannealing as well as any other post-treating means. The temperature ispreferably 200-500° C., and the temperature ramp rate is from 0.1 to 100deg ° C./min. The total annealing time is preferably from 0.01 min to 12hours.

Chemical treatment of the OSG film is conducted under the followingconditions.

The use of fluorinating (HF, SIF₄, NF₃, F₂, COF₂, CO₂F₂, etc.),oxidizing (H₂O₂, O₃, etc.), chemical drying, methylating, or otherchemical treatments that enhance the properties of the final material.Chemicals used in such treatments can be in solid, liquid, gaseousand/or supercritical fluid states.

Supercritical fluid post-treatment for selective removal of porogensfrom an organosilicate film is conducted under the following conditions.

The fluid can be carbon dioxide, water, nitrous oxide, ethylene, SF₆,and/or other types of chemicals. Other chemicals can be added to thesupercritical fluid to enhance the process. The chemicals can be inert(e.g., nitrogen, CO₂, noble gases (He, Ar, Ne, Kr, Xe), etc.), oxidizing(e.g., oxygen, ozone, nitrous oxide, etc.), or reducing (e.g., dilute orconcentrated hydrocarbons, hydrogen, etc.). The temperature ispreferably ambient to 500° C. The chemicals can also include largerchemical species such as surfactants. The total exposure time ispreferably from 0.01 min to 12 hours.

Plasma treating for selective removal of labile groups and possiblechemical modification of the OSG film is conducted under the followingconditions.

The environment can be inert (nitrogen, CO₂, noble gases (He, Ar, Ne,Kr, Xe), etc.), oxidizing (e.g., oxygen, air, dilute oxygenenvironments, enriched oxygen environments, ozone, nitrous oxide, etc.),or reducing (e.g., dilute or concentrated hydrogen, hydrocarbons(saturated, unsaturated, linear or branched, aromatics), etc.). Theplasma power is preferably 0-5000 W. The temperature is preferablyambient to 500° C. The pressure is preferably 10 mtorr to atmosphericpressure. The total curing time is preferably 0.01 min to 12 hours.

Photocuring for selective removal of porogens from an organosilicatefilm is conducted under the following conditions.

The environment can be inert (e.g., nitrogen, CO₂, noble gases (He, Ar,Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air, dilute oxygenenvironments, enriched oxygen environments, ozone, nitrous oxide, etc.),or reducing (e.g., dilute or concentrated hydrocarbons, hydrogen, etc.).The temperature is preferably ambient to 500° C. The power is preferably0 to 5000 W. The wavelength is preferably IR, visible, UV or deep UV(wavelengths<200 nm). The total curing time is preferably 0.01 min to 12hours.

Microwave post-treatment for selective removal of porogens from anorganosilicate film is conducted under the following conditions.

The environment can be inert (e.g., nitrogen, CO₂, noble gases (He, Ar,Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air, dilute oxygenenvironments, enriched oxygen environments, ozone, nitrous oxide, etc.),or reducing (e.g., dilute or concentrated hydrocarbons, hydrogen, etc.).The temperature is preferably ambient to 500° C. The power andwavelengths are varied and tunable to specific bonds. The total curingtime is preferably from 0.01 min to 12 hours.

Electron beam post-treatment for selective removal of porogens orspecific chemical species from an organosilicate film and/or improvementof film properties is conducted under the following conditions.

The environment can be vacuum, inert (e.g., nitrogen, CO₂, noble gases(He, Ar, Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air, dilute oxygenenvironments, enriched oxygen environments, ozone, nitrous oxide, etc.),or reducing (e.g., dilute or concentrated hydrocarbons, hydrogen, etc.).The temperature is preferably ambient to 500° C. The electron densityand energy can be varied and tunable to specific bonds. The total curingtime is preferably from 0.001 min to 12 hours, and may be continuous orpulsed. Additional guidance regarding the general use of electron beamsis available in publications such as: S. Chattopadhyay et al., Journalof Materials Science, 36 (2001) 4323-4330; G. Kloster et al.,Proceedings of IITC, Jun. 3-5, 2002, SF, CA; and U.S. Pat. Nos.6,207,555 B1, 6,204,201 B1 and 6,132,814 A1. The use of electron beamtreatment may provide for porogen removal and enhancement of filmmechanical properties through bond-formation processes in matrix.

The invention will be illustrated in more detail with reference to thefollowing Examples, but it should be understood that the presentinvention is not deemed to be limited thereto.

EXAMPLES

All experiments were performed on an Applied Materials Precision-5000system in a 200 mm DxZ chamber fitted with an Advance Energy 2000 rfgenerator, using an undoped TEOS process kit. The recipe involved thefollowing basic steps: initial set-up and stabilization of gas flows,deposition, and purge/evacuation of chamber prior to wafer removal.Films were annealed in a tube furnace at 425° C. for 4 hours under N₂.

Thickness and refractive index were measured on an SCI Filmtek 2000Reflectometer. Dielectric constants were determined using Hg probetechnique on low resistivity p-type wafers (<0.02 ohm-cm). Mechanicalproperties were determined using MTS Nano Indenter. Thermal stabilityand off-gas products were determined by thermogravimetric analysis on aThermo TA Instruments 2050 TGA. Compositional data were obtained byx-ray photoelectron spectroscopy (XPS) on a Physical Electronics 5000LS.The atomic % values reported in the tables do not include hydrogen.

Three routes were chosen for introducing porosity into an OSG film. Thefirst route investigated to produce low k films with k<2.6 co-depositeda thermally labile organic oligomer as the porogen along with the OSG byplasma enhanced chemical vapor deposition (PECVD) and then removed theoligomer post-deposition in a thermal annealing step.

Example 1A

Alpha-terpinene (ATP) was co-deposited with diethoxymethylsilane (DEMS)onto a silicon wafer via PECVD in an oxidant-free environment. Theprocess conditions were 700 miligrams per minute (mgm) flow of a 39.4%(by volume) mixture of ATP in DEMS. A carrier gas flow of 500 sccm ofCO₂ was used to escort the chemicals into the deposition chamber.Further process conditions were as follows: a chamber pressure of Torr,wafer chuck temperature of 150° C., showerhead to wafers spacing of 0.26inches, and plasma power of 300 watts for a period of 180 seconds. Thefilm as deposited had a thickness of 650 nm and a dielectric constant of2.8. The film was annealed at 425° C. under nitrogen for 4 hours toremove substantially all of the incorporated ATP, as evidenced by XPS.FIG. 1 shows infrared spectra of the film before (dashed line) and after(solid line) annealing, indicating the elimination of the porogen. Theannealed film had a thickness of 492 nm and a dielectric constant of 2.4(see Table 2 below). FIG. 4 shows a thermogravimetric analysis of thefilm to demonstrate weight loss occurring during thermal treatments.

Example 1B

ATP was co-deposited with DEMS onto a silicon wafer via PECVD in anoxidant-free environment. The process conditions were 1300 miligrams perminute (mgm) flow of a 70% (by volume) mixture of alpha-terpinene inDEMS. A carrier gas flow of 500 sccm of CO₂ was used to entrain thechemicals into the gas flow into the deposition chamber. Further processconditions were as follows: a chamber pressure of 8 Torr, wafer chucktemperature of 200° C., showerhead to wafers spacing of 0.30 inches, andplasma power of 600 watts for a period of 120 seconds. The film asdeposited had a thickness of 414 nm and a dielectric constant of 2.59.The film was annealed at 425° C. under nitrogen for 4 hours to removesubstantially all the incorporated ATP. The annealed film had athickness of 349 nm and a dielectric constant of 2.14 (see Table 2below).

Example 1C

A film was prepared and annealed substantially in accordance withExample 1A except that the anneal was conducted at a reduced temperatureof 400° C. The infrared spectrum of the resulting film, includingwavenumbers, is shown in FIG. 2. The infrared spectrum of the porogen,ATP, is shown in FIG. 3 for comparison.

Example 1D Comparative

A film was prepared and annealed substantially in accordance withExample 1A except that no porogens were used. The film had a dielectricconstant of 2.8, and a composition substantially identical to theannealed film of Example 1A (see Tables 1 and 2).

Example 1E Comparative

A film was prepared and annealed substantially in accordance withExample 1D except that the plasma power was 400 watts. The film had adielectric constant of 2.8, and a composition substantially identical tothe annealed film of Example 1A (see Tables 1 and 2).

Example 1F

A film was prepared and annealed substantially in accordance withExample 1A except that the process conditions were 1000 miligrams perminute (mgm) flow of a 75% (by volume) mixture of alpha-terpinene (ATP)in di-t-butoxymethylsilane (DtBOMS). A carrier gas flow of 500 sccm ofCO₂ was used to escort the chemicals into the deposition chamber.Further process conditions were as follows: a chamber pressure of 7Torr, wafer chuck temperature of 215° C., showerhead to wafers spacingof 0.30 inches, and plasma power of 400 watts for a period of 240seconds. The film as deposited had a thickness of 540 nm and adielectric constant of 2.8. The film was annealed at 425° C. undernitrogen for 4 hours to remove substantially all the incorporatedalpha-terpinene. The annealed film had a thickness of 474 nm and adielectric constant of 2.10. The modulus and hardness were 2.23 and 0.18GPa, respectively.

Example 1G

ATP was co-deposited with DtBOMS onto a silicon wafer via PECVD in anoxidant-free environment. The process conditions were 700 miligrams perminute (mgm) flow of a 75% (by volume) mixture of ATP in DtBOMS. Acarrier gas flow of 500 sccm of CO₂ was used to escort the chemicalsinto the deposition chamber. Further process conditions were as follows:a chamber pressure of 9 Torr, wafer chuck temperature of 275° C.,showerhead to wafers spacing of 0.30 inches, and plasma power of 600watts for a period of 240 seconds. The film as deposited had a thicknessof 670 nm and a dielectric constant of 2.64. The film was annealed at425° C. under nitrogen for 4 hours to remove substantially all theincorporated ATP. The annealed film had a thickness of 633 nm and adielectric constant of 2.19. The modulus and hardness were 3.40 and 0.44GPa, respectively.

Example 2

The second route investigated to produce low k films with k<2.6 used asingle source organosilane precursor which included a thermally labileorganic functionality as part of the molecular structure. The potentialadvantage of attaching the thermally labile group to a silica precursoris improved incorporation of the thermally labile group into the film.In order to investigate this route, we synthesized the moleculeneo-hexyl-tetramethylcyclotetrasiloxane (neo-hexyl-TMCTS), in which aneo-hexyl group was grafted onto the TMCTS framework. The processconditions used in this test were 500 mgm flow of neohexyl-TMCTS and acarrier gas flow of 500 sccm of CO₂, a chamber pressure of 6 Torr, waferchuck temperature of 150° C., showerhead to wafers spacing of 0.32inches, and plasma power of 300 watts for a period of 90 seconds.Thickness of the as-deposited film was 1120 nm with a dielectricconstant of 2.7. The film was annealed at 425° C. for 4 hours under N₂.Film thickness was reduced to 710 nm and the dielectric constant to 2.5.Films deposited from the TMCTS at 150° C. had a dielectric constantas-deposited of 2.8, which did not change after thermal annealing at425° C. for 4 hours.

Example 3

A third route investigated to produce low k films with k<2.6 was tophysically mix an organosilicon precursor with a silica precursor havinga large thermally labile group attached to it. To prove the efficacy ofthis route, fufuroxydimethylsilane was co-deposited with TMCTS at thefollowing conditions; 1000 mgm flow of an 11% mixture offurfuroxydimethylsilane in TMCTS and a carrier gas flow of 500 sccm ofHe, a chamber pressure of 6 Torr, wafer chuck temperature of 150° C.,showerhead to wafers spacing of 0.26 inches, and plasma power of 300watts for a period of 40 seconds. Thickness of the as-deposited film was1220 nm with a dielectric constant of 3.0. The inclusion of thefurfuroxy was indicated by FTIR in the as-deposited films. After thermalpost-treatments at 400° C. in nitrogen for 1 hour the k was reduced to2.73. It is likely in this case that there was remaining a significantportion of the incorporated furfuroxy groups even after thermal anneal.

The preceding examples indicate the ability to incorporate a variety offunctional groups into as-deposited films, and more critically theimportance of the proper choice of the porogen to enable materials withk<2.6. A variety of other porogens can also function using these routes.To provide optimum low dielectric constant materials with k<2.6 requiresgood network-forming organosilane/organosiloxane precursors which canprovide the proper type and amount of organic-group incorporation in theOSG network. It is preferred that network-forming precursors which donot require the addition of oxidant to produce OSG films be used. Thisis of particular importance when using hydrocarbon-based pore-formingprecursors which are susceptible to oxidation. Oxidation may causesignificant modification of the pore-former during deposition whichcould hamper its ability to be subsequently removed during annealingprocesses.

TABLE 1 XPS Data Example Description C O N Si Conditions 1A DEMS-ATP51.8 25.6 ND 22.6 150° C., 300 W 1A Annealed 24.5 43.1 ND 32.4 425° C.,4 hrs. 1E DEMS 28.8 38.8 ND 32.4 150° C., 400 W 1E Annealed 25.1 41.4 ND33.5 425° C., 4 hrs. 1D DEMS 27.0 40.6 ND 32.4 150° C., 300 W 1DAnnealed 23.4 42.7 ND 33.9 425° C., 4 hrs. all compositional analysisafter 30 sec Ar sputter to clean surface; inherent measurement error +/−2 atomic %. Note: Hydrogen cannot be determined by XPS; atomiccompositions shown are normalized without hydrogen

TABLE 2 Film Property Data Refractive Δ Thickness Example Description KIndex (%) H (GPa) M (GPa) 1D; 1E Various DEMS 2.9-3.1 1.435 — 0.30-0.472.4-3.5 (as-deposited) 1D; 1E Various DEMS 2.80 1.405 7-10 — —(post-treated) 1A DEMS-ATP (as- 2.80 1.490 — — — deposited) 1A DEMS-2.41 1.346 22 0.36 3.2 ATP (post- treated) 1B DEMS-ATP (as- 2.59 — — —deposited) 1B DEMS-ATP 2.14 16 (post-treated) 1F DtBOMS-ATP 2.80 1.491 —— — (as-deposited) 1F DtBOMS-ATP 2.10 1.315 12 0.18 2.2 (post-treated)1G DtBOMS-ATP 2.64 1.473 — — — (as-deposited) 1G DtBOMS-ATP 2.19 1.3345.5 0.44 3.4 (psot-treated) Note: all depositions performed at 150° C.,hardness (H) and modulus (M) determined by nanoindentation.

Comparison of the IR spectrum of as-deposited and N₂ thermalpost-treated DEMS/ATP films shows that thermal post-treatment in aninert atmosphere is successful for selective removal of porogen andretention of the OSG lattice. There is essentially no change in theS₁—CH₃ absorption at 1275 cm¹ after thermal anneal (the S₁—CH₃ isassociated with the OSG network). However, there is seen a dramaticreduction in C—H absorptions near 3000 cm⁻¹ suggesting that essentiallyall the carbon associated with ATP has been removed. The IR spectrum forATP is shown for reference in FIG. 3. An added benefit of this annealappears to be a significant reduction in the Si—H absorption at 2240 and2170 cm⁻¹ which should render the film more hydrophobic. Thus, incertain embodiments of the invention, each Si atom of the film is bondedto not more than one H atom. However, in other embodiments, the numberof H atoms bonded to Si atoms is not so limited.

Compositional analysis indicates that the DEMS-ATP film after anneal at425° C. for 4 hrs (Example 1A) has essentially identical composition toa DEMS films deposited and annealed in the same manner (Example 1D). TheDEMS-ATP film prior to anneal indicates a substantially larger amount ofcarbon-based material in the film (IR analysis supports that thiscarbon-based material is very similar to ATP—see FIG. 3). This supportsthe assertion that the porogen material incorporated into a DEMS filmwhen co-deposited with ATP is essentially completely removed by thethermal post-treatment process. Thermogravimetric analysis (FIG. 4)further indicates that significant weight loss of the as-depositedmaterial is experienced when heated to temperatures above 350° C., whichis additional proof of porogen removal during annealing. The observedfilm shrinkage is likely caused by collapse of some portion of the OSGnetwork upon removal of the porogen. However, there is little loss oforganic groups from the OSG network, i.e., terminal methyl groups withinthe DEMS are mostly retained (see the XPS data of pre and post thermaltreatment for DEMS film shown in Table 1). This is supported by therelatively equivalent S₁—CH₃ bands at ˜1275 wavenumbers in the IRspectrum. Hydrophobicity of this material is substantiated by the lackof Si—OH groups in the IR spectrum. The decrease in refractive index anddielectric constants of the films post-annealing suggests that they areless dense than the pre-annealed film, despite the decrease in filmthickness. Positron Annihilation Lifetime Spectroscopy (PALS) indicatespore sizes for samples 1A, 1B, and 1F in the range of ˜1.5 nm equivalentspherical diameter. Also, unlike the work of Grill et al (referenced inthe introduction), analysis of the thickness loss in conjunction withthe compositional change (Example 1A) indicates that the OSG network isretained during anneal and not significantly degraded.

The present invention has been set forth with regard to severalpreferred embodiments, but the scope of the present invention isconsidered to be broader than those embodiments and should beascertained from the claims below.

1. A chemical vapor deposition method for producing a porousorganosilica glass film, said method comprising: providing a substratewithin a chamber; introducing into the chamber gaseous reagentscomprising: at least one silicon containing precursor having the formulaR¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) where R¹ and R³ are independently H or C₁to C₄ linear or branched, saturated, singly or multiply unsaturated,cyclic, partially or fully fluorinated hydrocarbon; R², R⁶ and R⁷ areindependently C₁ to C₆ linear or branched, saturated, singly or multiplyunsaturated, cyclic, aromatic, partially or fully fluorinatedhydrocarbon, R⁴ and R⁵ are independently H, C₁ to C₆ linear or branched,saturated, singly or multiply unsaturated, cyclic, aromatic, partiallyor fully fluorinated hydrocarbon, n is 0 to 3, m is 0 to 3, q is 0 to 3and p is 0 to 3, provided that n+m≧1, n+p≦3, and m+q≦3 and optionallydiethoxymethylsilane; and at least one porogen selected from the groupconsisting of: (i) at least one bicyclic hydrocarbon having a bicyclicstructure and the formula C_(n)H_(2n−2), where n is 4 to 14, a number ofcarbons in the bicyclic structure is from 4 to 12, and the at least onebicyclic hydrocarbon optionally contains a plurality of simple orbranched hydrocarbons substituted onto the bicyclic structure; and (ii)at least one multiply unsaturated bicyclic hydrocarbon having a bicyclicstructure and the formula C_(n)H_(2n−(2+2x)), where x is a number ofunsaturated sites, n is 4 to 14, a number of carbons in the bicyclicstructure is from 4 to 12, and the at least one multiply unsaturatedbicyclic hydrocarbon optionally contains a plurality of simple orbranched hydrocarbons substituents substituted onto the bicyclicstructure, and contains endocyclic unsaturation or unsaturation on oneof the hydrocarbon substituents; applying energy to the gaseous reagentsin the chamber to induce reaction of the gaseous reagents to deposit apreliminary film on the substrate, wherein the preliminary film containsthe porogen; and removing from the preliminary film substantially all ofthe porogen to provide the porous film with pores and a dielectricconstant less than 2.6.
 2. The method of claim 1, wherein thesilicon-containing precursor further comprises diethoxymethylsilane. 3.The method of claim 1, where in the at least one silicon containingprecursor having the formula R¹ _(n)(OR²)_(p)(O(O)CR⁴)_(3−n−p)Si—R⁷—SiR³_(m)(O(O)CR⁵)_(q)(OR⁶)_(3−m−q) comprises bis(trimethoxysilyl)methane. 4.The method of claim 1 wherein the at least one porogen is selected fromthe group consisting of: norbornadiene, norbornene, norbornane, decalin,and naphthalene.
 5. The method of claim 1, wherein the dielectricconstant is less than 1.9.
 6. The method of claim 1, wherein most of thehydrogen in the porous film is bonded to carbon.
 7. The method of claim1, wherein the porous film has a density less than 1.5 g/ml.
 8. Themethod of claim 1, wherein the pores have an equivalent sphericaldiameter less than or equal to 5 nm.
 9. The method of claim 1, wherein aFourier transform infrared (FTIR) spectrum of the porous film issubstantially identical to a reference FTIR of a reference film preparedby a process substantially identical to the method except for a lack ofany porogen.
 10. The method of claim 9, wherein the porous film has adielectric constant at least 0.3 less than a reference dielectricconstant of the reference film.
 11. The method of claim 9, wherein theporous film has a density at least 10% less than a reference density ofthe reference film.
 12. The method of claim 1, wherein the porous filmhas an average weight loss of less than 1.0 wt %/hr isothermal at 425°C. under N₂.
 13. The method of claim 1, wherein the porous film has anaverage weight loss of less than 1.0 wt %/hr isothermal at 425° C. underair.
 14. The method of claim 1, further comprising treating thepreliminary film with at least one post-treating agent selected from thegroup consisting of thermal energy, plasma energy, photon energy,electron energy, microwave energy and chemicals, wherein the at leastone post-treating agent removes from the preliminary film substantiallyall of the porogen to provide the porous organosilica glass film withpores and a dielectric constant less than 2.6.
 15. The method of claim14, wherein the at least one post-treating agent improves a property ofthe resulting porous organosilica glass film before, during and/or afterremoving substantially all of the porogen from the preliminary film. 16.The method of claim 15, wherein an additional post-treating agentimproves a property of the resulting porous organosilica glass filmbefore, during and/or after the at least one post-treating agent removessubstantially all of the porogen from the preliminary film.
 17. Themethod of claim 14, wherein the at least one post-treating agent iselectron energy provided by an electron beam.
 18. The method of claim14, wherein the at least one post-treating agent is photon energy. 19.The method of claim 14, wherein the at least one post-treating agent isthermal energy.
 20. The method of claim 14, wherein the at least onepost-treating agent is a supercritical fluid.